freebsd-nq/sys/scsi/sd.c

/*
 * Written by Julian Elischer (julian@dialix.oz.au)
 * for TRW Financial Systems for use under the MACH(2.5) operating system.
 *
 * TRW Financial Systems, in accordance with their agreement with Carnegie
 * Mellon University, makes this software available to CMU to distribute
 * or use in any manner that they see fit as long as this message is kept with
 * the software. For this reason TFS also grants any other persons or
 * organisations permission to use or modify this software.
 *
 * TFS supplies this software to be publicly redistributed
 * on the understanding that TFS is not responsible for the correct
 * functioning of this software in any circumstances.
 *
 * Ported to run under 386BSD by Julian Elischer (julian@dialix.oz.au) Sept 1992
 *
 *      $Id: sd.c,v 1.107 1997/08/09 01:44:22 julian Exp $
 */

#include "opt_bounce.h"
#include "opt_scsi.h"

#define SPLSD splbio
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/dkbad.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/disklabel.h>
#include <sys/diskslice.h>
#include <sys/dkstat.h>
#include <sys/conf.h>
#ifdef DEVFS
#include <sys/devfsext.h>
#endif /*DEVFS*/

#include <scsi/scsi_disk.h>
#include <scsi/scsiconf.h>
#include <scsi/scsi_debug.h>
#include <scsi/scsi_driver.h>

#include <vm/vm.h>
#include <vm/vm_prot.h>
#include <vm/pmap.h>
#include <machine/md_var.h>
#include <i386/i386/cons.h>		/* XXX *//* for aborting dump */
#ifdef PC98
#include <pc98/pc98/pc98_machdep.h>
#endif

static u_int32_t sdstrats, sdqueues;

#define SECSIZE 512
#ifdef PC98
#define	SDOUTSTANDING	2
#else
#define	SDOUTSTANDING	4
#endif
#define	SD_RETRIES	4
#define	MAXTRANSFER	8		/* 1 page at a time */

#define	PARTITION(dev)	dkpart(dev)
#define	SDUNIT(dev)	dkunit(dev)

/* XXX introduce a dkmodunit() macro for this. */
#define SDSETUNIT(DEV, U) \
 makedev(major(DEV), dkmakeminor((U), dkslice(DEV), dkpart(DEV)))

static errval	sd_get_parms __P((int unit, int flags));
static errval	sd_reassign_blocks __P((int unit, int block));
static u_int32_t	sd_size __P((int unit, int flags));
static	void	sdstrategy1 __P((struct buf *));

static int		sd_sense_handler __P((struct scsi_xfer *));
static void    sdstart __P((u_int32_t, u_int32_t));

struct scsi_data {
	u_int32_t flags;
#define	SDINIT		0x04	/* device has been init'd */
	struct disk_parms {
		u_char  heads;	/* Number of heads */
		u_int16_t cyls;	/* Number of cylinders */
		u_char  sectors;	/*dubious *//* Number of sectors/track */
		u_int16_t secsiz;	/* Number of bytes/sector */
		u_int32_t disksize;	/* total number sectors */
	} params;
	struct diskslices *dk_slices;	/* virtual drives */
	struct buf_queue_head buf_queue;
	int dkunit;		/* disk stats unit number */
#ifdef	DEVFS
	void	*b_devfs_token;
	void	*c_devfs_token;
	void	*ctl_devfs_token;
#endif
};

static int sdunit(dev_t dev) { return SDUNIT(dev); }
static dev_t sdsetunit(dev_t dev, int unit) { return SDSETUNIT(dev, unit); }

static errval sd_open __P((dev_t dev, int mode, int fmt, struct proc *p,
		    struct scsi_link *sc_link));
static errval sd_ioctl(dev_t dev, int cmd, caddr_t addr, int flag,
		struct proc *p, struct scsi_link *sc_link);
static errval sd_close __P((dev_t dev, int fflag, int fmt, struct proc *p,
		     struct scsi_link *sc_link));
static void sd_strategy(struct buf *bp, struct scsi_link *sc_link);

static	d_open_t	sdopen;
static	d_close_t	sdclose;
static	d_ioctl_t	sdioctl;
static	d_dump_t	sddump;
static	d_psize_t	sdsize;
static	d_strategy_t	sdstrategy;

#define CDEV_MAJOR 13
#define BDEV_MAJOR 4
static struct cdevsw sd_cdevsw;
static struct bdevsw sd_bdevsw = 
	{ sdopen,	sdclose,	sdstrategy,	sdioctl,	/*4*/
	  sddump,	sdsize,		D_DISK,	"sd",	&sd_cdevsw,	-1 };



SCSI_DEVICE_ENTRIES(sd)

static struct scsi_device sd_switch =
{
	sd_sense_handler,
	sdstart,			/* have a queue, served by this */
	NULL,			/* have no async handler */
	NULL,			/* Use default 'done' routine */
	"sd",
	0,
	{0, 0},
	0,				/* Link flags */
	sdattach,
	"Direct-Access",
	sdopen,
	sizeof(struct scsi_data),
	T_DIRECT,
	sdunit,
	sdsetunit,
	sd_open,
	sd_ioctl,
	sd_close,
	sd_strategy,
};

static struct scsi_xfer sx;


static inline void
sd_registerdev(int unit)
{
	if(dk_ndrive < DK_NDRIVE) {
		sprintf(dk_names[dk_ndrive], "sd%d", unit);
		dk_wpms[dk_ndrive] = (8*1024*1024/2);
		SCSI_DATA(&sd_switch, unit)->dkunit = dk_ndrive++;
	} else {
		SCSI_DATA(&sd_switch, unit)->dkunit = -1;
	}
}


/*
 * The routine called by the low level scsi routine when it discovers
 * a device suitable for this driver.
 */
static errval
sdattach(struct scsi_link *sc_link)
{
	u_int32_t unit;
	struct disk_parms *dp;
#ifdef DEVFS
	int	mynor;
#endif

	struct scsi_data *sd = sc_link->sd;

	unit = sc_link->dev_unit;

	dp = &(sd->params);

	if (sc_link->opennings > SDOUTSTANDING)
		sc_link->opennings = SDOUTSTANDING;

	TAILQ_INIT(&sd->buf_queue);
	/*
	 * Use the subdriver to request information regarding
	 * the drive. We cannot use interrupts yet, so the
	 * request must specify this.
	 */
	sd_get_parms(unit, SCSI_NOSLEEP | SCSI_NOMASK);
	/*
	 * if we don't have actual parameters, assume 512 bytes/sec
	 * (could happen on removable media - MOD)
	 * -- this avoids the division below from falling over
	 */
	if(dp->secsiz == 0) dp->secsiz = SECSIZE;
	printf("%ldMB (%ld %d byte sectors)",
	    dp->disksize / ((1024L * 1024L) / dp->secsiz),
	    dp->disksize,
	    dp->secsiz);

#ifndef SCSI_REPORT_GEOMETRY
	if ( (sc_link->flags & SDEV_BOOTVERBOSE) )
#endif
	{
		sc_print_addr(sc_link);
		printf("with %d cyls, %d heads, and an average %d sectors/track",
	   	dp->cyls, dp->heads, dp->sectors);
	}

	sd->flags |= SDINIT;
	sd_registerdev(unit);

#ifdef DEVFS
	mynor = dkmakeminor(unit, WHOLE_DISK_SLICE, RAW_PART);
	sd->b_devfs_token = devfs_add_devswf(&sd_bdevsw, mynor, DV_BLK,
					     UID_ROOT, GID_OPERATOR, 0640,
					     "sd%d", unit);
	sd->c_devfs_token = devfs_add_devswf(&sd_cdevsw, mynor, DV_CHR,
					     UID_ROOT, GID_OPERATOR, 0640,
					     "rsd%d", unit);
	mynor = dkmakeminor(unit, 0, 0);	/* XXX */
	sd->ctl_devfs_token = devfs_add_devswf(&sd_cdevsw,
					       mynor | SCSI_CONTROL_MASK,
					       DV_CHR,
					       UID_ROOT, GID_WHEEL, 0600,
					       "rsd%d.ctl", unit);
#endif

	return 0;
}

/*
 * open the device. Make sure the partition info is a up-to-date as can be.
 */
static errval
sd_open(dev, mode, fmt, p, sc_link)
	dev_t	dev;
	int	mode;
	int	fmt;
	struct proc *p;
	struct scsi_link *sc_link;
{
	errval  errcode = 0;
	u_int32_t unit;
	struct disklabel label;
	struct scsi_data *sd;

	unit = SDUNIT(dev);
	sd = sc_link->sd;

	/*
	 * Make sure the disk has been initialised
	 * At some point in the future, get the scsi driver
	 * to look for a new device if we are not initted
	 */
	if ((!sd) || (!(sd->flags & SDINIT))) {
		return (ENXIO);
	}

	SC_DEBUG(sc_link, SDEV_DB1,
	    ("sd_open: dev=0x%lx (unit %ld, partition %d)\n",
		dev, unit, PARTITION(dev)));

	/*
	 * "unit attention" errors should occur here if the
	 * drive has been restarted or the pack changed.
	 * just ingnore the result, it's a decoy instruction
	 * The error handlers will act on the error though
	 * and invalidate any media information we had.
	 */
	scsi_test_unit_ready(sc_link, 0);

	errcode = scsi_device_lock(sc_link);
	if (errcode)
		return errcode;

	/*
	 * If it's been invalidated, then forget the label
	 */
	sc_link->flags |= SDEV_OPEN;	/* unit attn becomes an err now */
	if (!(sc_link->flags & SDEV_MEDIA_LOADED) && sd->dk_slices != NULL) {
		/*
		 * If somebody still has it open, then forbid re-entry.
		 */
		if (dsisopen(sd->dk_slices)) {
			errcode = ENXIO;
			goto bad;
		}

		dsgone(&sd->dk_slices);
	}
	/*
	 * In case it is a funny one, tell it to start
	 * not needed for  most hard drives (ignore failure)
	 */
	scsi_start_unit(sc_link, SCSI_ERR_OK | SCSI_SILENT);

	/*
	 * Check that it is still responding and ok.
	 */
	if (scsi_test_unit_ready(sc_link, 0)) {
		SC_DEBUG(sc_link, SDEV_DB3, ("device not reponding\n"));
		errcode = ENXIO;
		goto bad;
	}
	SC_DEBUG(sc_link, SDEV_DB3, ("device ok\n"));

	/*
	 * Load the physical device parameters
	 */
	if(errcode = sd_get_parms(unit, 0))	/* sets SDEV_MEDIA_LOADED */
		goto bad;
	switch (sd->params.secsiz) {
	case 512:
	case 1024:
	case 2048:
		break;
	default:
		printf("sd%ld: Can't deal with %d bytes logical blocks\n",
		    unit, sd->params.secsiz);
		Debugger("sd");
		errcode = ENXIO;
		goto bad;
	}

	SC_DEBUG(sc_link, SDEV_DB3, ("Params loaded "));

	/* Lock the pack in. */
	scsi_prevent(sc_link, PR_PREVENT, SCSI_ERR_OK | SCSI_SILENT);

	/* Build label for whole disk. */
	bzero(&label, sizeof label);
	label.d_secsize = sd->params.secsiz;
	label.d_nsectors = sd->params.sectors;
	label.d_ntracks = sd->params.heads;
	label.d_ncylinders = sd->params.cyls;
	label.d_secpercyl = sd->params.heads * sd->params.sectors;
	if (label.d_secpercyl == 0)
		label.d_secpercyl = 100;
		/* XXX as long as it's not 0 - readdisklabel divides by it (?) */
	label.d_secperunit = sd->params.disksize;

	/* Initialize slice tables. */
	errcode = dsopen("sd", dev, fmt, &sd->dk_slices, &label, sdstrategy1,
			 (ds_setgeom_t *)NULL, &sd_bdevsw, &sd_cdevsw);
	if (errcode != 0)
		goto bad;
	SC_DEBUG(sc_link, SDEV_DB3, ("Slice tables initialized "));

	SC_DEBUG(sc_link, SDEV_DB3, ("open %ld %ld\n", sdstrats, sdqueues));

	scsi_device_unlock(sc_link);
	return 0;

bad:
	if (!dsisopen(sd->dk_slices)) {
		scsi_prevent(sc_link, PR_ALLOW, SCSI_ERR_OK | SCSI_SILENT);
		sc_link->flags &= ~SDEV_OPEN;
	}
	scsi_device_unlock(sc_link);
	return errcode;
}

/*
 * close the device.. only called if we are the LAST occurence of an open
 * device.  Convenient now but usually a pain.
 */
static errval
sd_close(dev, fflag, fmt, p, sc_link)
	dev_t	dev;
	int	fflag;
	int	fmt;
	struct proc *p;
	struct scsi_link *sc_link;
{
	struct scsi_data *sd;
	errval errcode;

	sd = sc_link->sd;
	errcode = scsi_device_lock(sc_link);
	if (errcode)
		return errcode;
	dsclose(dev, fmt, sd->dk_slices);
	if (!dsisopen(sd->dk_slices)) {
		scsi_prevent(sc_link, PR_ALLOW, SCSI_SILENT | SCSI_ERR_OK);
		sc_link->flags &= ~SDEV_OPEN;
	}
	scsi_device_unlock(sc_link);
	return (0);
}

/*
 * Actually translate the requested transfer into one the physical driver
 * can understand.  The transfer is described by a buf and will include
 * only one physical transfer.
 */
static void
sd_strategy(struct buf *bp, struct scsi_link *sc_link)
{
	u_int32_t opri;
	struct scsi_data *sd;
	u_int32_t unit, secsize;

	sdstrats++;
	unit = SDUNIT((bp->b_dev));
	sd = sc_link->sd;
	/*
	 * If the device has been made invalid, error out
	 */
	if (!(sc_link->flags & SDEV_MEDIA_LOADED)) {
		bp->b_error = EIO;
		goto bad;
	}

	/*
	 * check it's not too big a transfer for our adapter
	 */
        scsi_minphys(bp,&sd_switch);

	/*
	 * Odd number of bytes or negative offset
	 */
	if (bp->b_blkno < 0 ) {
		bp->b_error = EINVAL;
		printf("sd_strategy: Negative block number: 0x%x\n",
			bp->b_blkno);
		goto bad;
	}

	secsize = sd->params.secsiz;

	/* make sure the blkno is scalable */
	if( (bp->b_blkno % (secsize/DEV_BSIZE)) != 0 ) {
		bp->b_error = EINVAL;
		printf("sd_strategy: Block number is not multiple of sector size (2): 0x%x\n", bp->b_blkno);
		goto bad;
	}

	/* make sure that the transfer size is a multiple of the sector size */
	if( (bp->b_bcount % secsize) != 0 ) {
		bp->b_error = EINVAL;
		printf("sd_strategy: Invalid b_bcount %d at block number: 0x%x\n", bp->b_bcount, bp->b_blkno);
		goto bad;
	}

	/*
	 * Do bounds checking, adjust transfer, set b_cylin and b_pbklno.
	 */
	{
		int status;
		int sec_blk_ratio = secsize/DEV_BSIZE;
		/* save original block number and size */
		int b_blkno = bp->b_blkno;
		int b_bcount = bp->b_bcount;

		/* replace with scaled values */
		bp->b_blkno /= sec_blk_ratio;
		bp->b_bcount /= sec_blk_ratio;
	
		/* enforce limits and map to physical block number */
		status = dscheck(bp, sd->dk_slices);

		/* prevent bad side effects in block system */
		bp->b_blkno = b_blkno;
		bp->b_bcount = b_bcount;

		/* scale resid */
		bp->b_resid *= sec_blk_ratio;

		/* see if the mapping failed */
		if (status <= 0)
			goto done;	/* XXX check b_resid */
	}

	opri = SPLSD();
	/*
	 * Use a bounce buffer if necessary
	 */
#ifdef BOUNCE_BUFFERS
	if (sc_link->flags & SDEV_BOUNCE)
		vm_bounce_alloc(bp);
#endif

	/*
	 * Place it in the queue of disk activities for this disk
	 */
#ifdef SDDISKSORT
	tqdisksort(&sd->buf_queue, bp);
#else
	TAILQ_INSERT_TAIL(&sd->buf_queue, bp, b_act);
#endif

	/*
	 * Tell the device to get going on the transfer if it's
	 * not doing anything, otherwise just wait for completion
	 */
	sdstart(unit, 0);

	splx(opri);
	return /*0*/;
bad:
	bp->b_flags |= B_ERROR;
done:

	/*
	 * Correctly set the buf to indicate a completed xfer
	 */
	bp->b_resid = bp->b_bcount;
	biodone(bp);
	return /*0*/;
}

static void
sdstrategy1(struct buf *bp)
{
	/*
	 * XXX - do something to make sdstrategy() but not this block while
	 * we're doing dsinit() and dsioctl().
	 */
	sdstrategy(bp);
}

/*
 * sdstart looks to see if there is a buf waiting for the device
 * and that the device is not already busy. If both are true,
 * It dequeues the buf and creates a scsi command to perform the
 * transfer in the buf. The transfer request will call scsi_done
 * on completion, which will in turn call this routine again
 * so that the next queued transfer is performed.
 * The bufs are queued by the strategy routine (sdstrategy)
 *
 * This routine is also called after other non-queued requests
 * have been made of the scsi driver, to ensure that the queue
 * continues to be drained.
 *
 * must be called at the correct (highish) spl level
 * sdstart() is called at SPLSD  from sdstrategy and scsi_done
 */
static void
sdstart(u_int32_t unit, u_int32_t flags)
{
	register struct	scsi_link *sc_link = SCSI_LINK(&sd_switch, unit);
	register struct scsi_data *sd = sc_link->sd;
	struct buf *bp = NULL;
	struct scsi_rw_big cmd;
	u_int32_t blkno, nblk, secsize;

	SC_DEBUG(sc_link, SDEV_DB2, ("sdstart "));
	/*
	 * Check if the device has room for another command
	 */
	while (sc_link->opennings) {

		/*
		 * there is excess capacity, but a special waits
		 * It'll need the adapter as soon as we clear out of the
		 * way and let it run (user level wait).
		 */
		if (sc_link->flags & SDEV_WAITING) {
			return;
		}
		/*
		 * See if there is a buf with work for us to do..
		 */
		bp = sd->buf_queue.tqh_first;
		if (bp == NULL) {	/* yes, an assign */
			return;
		}
		TAILQ_REMOVE(&sd->buf_queue, bp, b_act);

		/*
		 *  If the device has become invalid, abort all the
		 * reads and writes until all files have been closed and
		 * re-openned
		 */
		if (!(sc_link->flags & SDEV_MEDIA_LOADED)) {
			goto bad;
		}
		/*
		 * We have a buf, now we know we are going to go through
		 * With this thing..
		 */
		secsize = sd->params.secsiz;
		blkno = bp->b_pblkno;
		if (bp->b_bcount & (secsize - 1))
		{
		    goto bad;
		}
		nblk = bp->b_bcount / secsize;

		/*
		 *  Fill out the scsi command
		 */
		cmd.op_code = (bp->b_flags & B_READ)
		    ? READ_BIG : WRITE_BIG;
		cmd.addr_3 = (blkno & 0xff000000UL) >> 24;
		cmd.addr_2 = (blkno & 0xff0000) >> 16;
		cmd.addr_1 = (blkno & 0xff00) >> 8;
		cmd.addr_0 = blkno & 0xff;
		cmd.length2 = (nblk & 0xff00) >> 8;
		cmd.length1 = (nblk & 0xff);
		cmd.byte2 = cmd.reserved = cmd.control = 0;
		/*
		 * Call the routine that chats with the adapter.
		 * Note: we cannot sleep as we may be an interrupt
		 */
		if (scsi_scsi_cmd(sc_link,
			(struct scsi_generic *) &cmd,
			sizeof(cmd),
			(u_char *) bp->b_un.b_addr,
			bp->b_bcount,
			SD_RETRIES,
			10000,
			bp,
			flags | ((bp->b_flags & B_READ) ?
			    SCSI_DATA_IN : SCSI_DATA_OUT))
		    == SUCCESSFULLY_QUEUED) {
			sdqueues++;
			if(sd->dkunit >= 0) {
				dk_xfer[sd->dkunit]++;
				dk_seek[sd->dkunit]++; /* don't know */
				dk_wds[sd->dkunit] += bp->b_bcount >> 6;
			}
		} else {
bad:
			printf("sd%ld: oops not queued\n", unit);
			bp->b_error = EIO;
			bp->b_flags |= B_ERROR;
			biodone(bp);
		}
	}
}

/*
 * Perform special action on behalf of the user
 * Knows about the internals of this device
 */
static errval
sd_ioctl(dev_t dev, int cmd, caddr_t addr, int flag, struct proc *p,
	 struct scsi_link *sc_link)
{
	/* struct sd_cmd_buf *args; */
	errval  error;
	struct scsi_data *sd;

	/*
	 * Find the device that the user is talking about
	 */
	sd = sc_link->sd;
	SC_DEBUG(sc_link, SDEV_DB1, ("sdioctl (0x%x)", cmd));

#if 0
	/* Wait until we have exclusive access to the device. */
	/* XXX this is how wd does it.  How did we work without this? */
	wdsleep(du->dk_ctrlr, "wdioct");
#endif

	/*
	 * If the device is not valid.. abandon ship
	 */
	if (!(sc_link->flags & SDEV_MEDIA_LOADED))
		return (EIO);

	if (cmd == DIOCSBAD)
		return (EINVAL);	/* XXX */
	
	error = scsi_device_lock(sc_link);
	if (error)
		return error;

	error = dsioctl("sd", dev, cmd, addr, flag, &sd->dk_slices,
			sdstrategy1, (ds_setgeom_t *)NULL);
	scsi_device_unlock(sc_link);
	if (error != -1)
		return (error);
	if (PARTITION(dev) != RAW_PART)
		return (ENOTTY);
	return (scsi_do_ioctl(dev, cmd, addr, flag, p, sc_link));
}

/*
 * Find out from the device what it's capacity is
 */
static u_int32_t
sd_size(unit, flags)
	int	unit, flags;
{
	struct scsi_read_cap_data rdcap;
	struct scsi_read_capacity scsi_cmd;
	u_int32_t size;
	struct scsi_link *sc_link = SCSI_LINK(&sd_switch, unit);

	/*
	 * make up a scsi command and ask the scsi driver to do
	 * it for you.
	 */
	bzero(&scsi_cmd, sizeof(scsi_cmd));
	scsi_cmd.op_code = READ_CAPACITY;

	/*
	 * If the command works, interpret the result as a 4 byte
	 * number of blocks
	 */
	if (scsi_scsi_cmd(sc_link,
		(struct scsi_generic *) &scsi_cmd,
		sizeof(scsi_cmd),
		(u_char *) & rdcap,
		sizeof(rdcap),
		SD_RETRIES,
		2000,
		NULL,
		flags | SCSI_DATA_IN) != 0) {
		printf("sd%d: could not get size\n", unit);
		return (0);
	} else {
		size = rdcap.addr_0 + 1;
		size += rdcap.addr_1 << 8;
		size += rdcap.addr_2 << 16;
		size += rdcap.addr_3 << 24;
	}
	return (size);
}

/*
 * Tell the device to map out a defective block
 */
static errval
sd_reassign_blocks(unit, block)
	int	unit, block;
{
	struct scsi_reassign_blocks scsi_cmd;
	struct scsi_reassign_blocks_data rbdata;
	struct scsi_link *sc_link = SCSI_LINK(&sd_switch, unit);

	bzero(&scsi_cmd, sizeof(scsi_cmd));
	bzero(&rbdata, sizeof(rbdata));
	scsi_cmd.op_code = REASSIGN_BLOCKS;

	rbdata.length_msb = 0;
	rbdata.length_lsb = sizeof(rbdata.defect_descriptor[0]);
	rbdata.defect_descriptor[0].dlbaddr_3 = ((block >> 24) & 0xff);
	rbdata.defect_descriptor[0].dlbaddr_2 = ((block >> 16) & 0xff);
	rbdata.defect_descriptor[0].dlbaddr_1 = ((block >> 8) & 0xff);
	rbdata.defect_descriptor[0].dlbaddr_0 = ((block) & 0xff);

	return (scsi_scsi_cmd(sc_link,
		(struct scsi_generic *) &scsi_cmd,
		sizeof(scsi_cmd),
		(u_char *) & rbdata,
		sizeof(rbdata),
		SD_RETRIES,
		5000,
		NULL,
		SCSI_DATA_OUT));
}
#define b2tol(a)	(((unsigned)(a##_1) << 8) + (unsigned)a##_0 )

/*
 * Get the scsi driver to send a full inquiry to the
 * device and use the results to fill out the disk
 * parameter structure.
 */
static errval
sd_get_parms(unit, flags)
	int	unit, flags;
{
	struct scsi_link *sc_link = SCSI_LINK(&sd_switch, unit);
	struct scsi_data *sd = sc_link->sd;
	struct disk_parms *disk_parms = &sd->params;
	struct scsi_mode_sense scsi_cmd;
	struct scsi_mode_sense_data {
		struct scsi_mode_header header;
		struct blk_desc blk_desc;
		union disk_pages pages;
	} scsi_sense;
	u_int32_t sectors;

	/*
	 * First check if we have it all loaded
	 */
	if (sc_link->flags & SDEV_MEDIA_LOADED)
		return 0;

	/*
	 * do a "mode sense page 4"
	 */
	bzero(&scsi_cmd, sizeof(scsi_cmd));
	scsi_cmd.op_code = MODE_SENSE;
	scsi_cmd.page = 4;
	scsi_cmd.length = 0x20;
#ifdef PC98
	if (sd_bios_parms(disk_parms, sc_link)) {
	} else
#endif
	/*
	 * If the command worked, use the results to fill out
	 * the parameter structure
	 */
	if (scsi_scsi_cmd(sc_link,
		(struct scsi_generic *) &scsi_cmd,
		sizeof(scsi_cmd),
		(u_char *) & scsi_sense,
		sizeof(scsi_sense),
		SD_RETRIES,
		4000,
		NULL,
		flags | SCSI_DATA_IN) != 0) {

		printf("sd%d could not mode sense (4).", unit);
		printf(" Using ficticious geometry\n");
		/*
		 * use adaptec standard ficticious geometry
		 * this depends on which controller (e.g. 1542C is
		 * different. but we have to put SOMETHING here..)
		 */
		sectors = sd_size(unit, flags);
		disk_parms->heads = 64;
		disk_parms->sectors = 32;
		disk_parms->cyls = sectors / (64 * 32);
		disk_parms->secsiz = SECSIZE;
		disk_parms->disksize = sectors;
	} else {

		SC_DEBUG(sc_link, SDEV_DB3,
		    ("%ld cyls, %d heads, %d precomp, %d red_write, %d land_zone\n",
			scsi_3btou(&scsi_sense.pages.rigid_geometry.ncyl_2),
			scsi_sense.pages.rigid_geometry.nheads,
			b2tol(scsi_sense.pages.rigid_geometry.st_cyl_wp),
			b2tol(scsi_sense.pages.rigid_geometry.st_cyl_rwc),
			b2tol(scsi_sense.pages.rigid_geometry.land_zone)));

		/*
		 * KLUDGE!!(for zone recorded disks)
		 * give a number of sectors so that sec * trks * cyls
		 * is <= disk_size
		 * can lead to wasted space! THINK ABOUT THIS !
		 */
		disk_parms->heads = scsi_sense.pages.rigid_geometry.nheads;
		disk_parms->cyls = scsi_3btou(&scsi_sense.pages.rigid_geometry.ncyl_2);
		disk_parms->secsiz = scsi_3btou(scsi_sense.blk_desc.blklen);

		sectors = sd_size(unit, flags);
		disk_parms->disksize = sectors;
		/* Check if none of these values are zero */
		if(disk_parms->heads && disk_parms->cyls) {
			sectors /= (disk_parms->heads * disk_parms->cyls);
		}
		else {
			/* set it to something reasonable */
			disk_parms->heads = 64;
			disk_parms->cyls = sectors / (64 * 32);
			sectors = 32;
		}
		/* keep secsiz sane too - we may divide by it later */
		if(disk_parms->secsiz == 0)
			disk_parms->secsiz = SECSIZE;
		disk_parms->sectors = sectors;	/* dubious on SCSI *//*XXX */
	}
	sc_link->flags |= SDEV_MEDIA_LOADED;
	return 0;
}

static int
sdsize(dev_t dev)
{
	struct scsi_data *sd;

	sd = SCSI_DATA(&sd_switch, (u_int32_t) SDUNIT(dev));
	if (sd == NULL)
		return (-1);
	return (dssize(dev, &sd->dk_slices, sdopen, sdclose));
}

/*
 * sense handler: Called to determine what to do when the
 * device returns a CHECK CONDITION.
 *
 * This will issue a retry when the device returns a
 * non-media hardware failure.  The CDC-WREN IV does this
 * when you access it during thermal calibrarion, so the drive
 * is pretty useless without this.
 *
 * In general, you probably almost always would like to issue a retry
 * for your disk I/O.  It can't hurt too much (the caller only retries
 * so many times) and it may save your butt.
 */

static int
sd_sense_handler(struct scsi_xfer *xs)
{
	struct scsi_sense_data *sense;
	struct scsi_inquiry_data *inqbuf;

	sense = &(xs->sense);

	/* I don't know what the heck to do with a deferred error,
	 * so I'll just kick it back to the caller.
	 */
	if ((sense->error_code & SSD_ERRCODE) == 0x71)
		return SCSIRET_CONTINUE;

	if (((sense->error_code & SSD_ERRCODE) == 0x70) &&
		((sense->ext.extended.flags & SSD_KEY) == 0x05))
		/* No point in retrying Illegal Requests */
			return SCSIRET_CONTINUE;

	inqbuf = &(xs->sc_link->inqbuf);

	/* It is dangerous to retry on removable drives without
	 * looking carefully at the additional sense code
	 * and sense code qualifier and ensuring the disk hasn't changed:
	 */
	if (inqbuf->dev_qual2 & SID_REMOVABLE)
		return SCSIRET_CONTINUE;

	/* Retry all disk errors.
	 */
	scsi_sense_print(xs);
	if (xs->retries)
		printf(", retries:%d\n", xs->retries);
	else
		printf(", FAILURE\n");

	return SCSIRET_DO_RETRY;
}

/*
 * dump all of physical memory into the partition specified, starting
 * at offset 'dumplo' into the partition.
 */
static errval
sddump(dev_t dev)
{				/* dump core after a system crash */
	struct disklabel *lp;
	register struct scsi_data *sd;	/* disk unit to do the IO */
	struct scsi_link *sc_link;
	int32_t	num;		/* number of sectors to write */
	u_int32_t	unit, part;
	int32_t	blkoff, blknum, blkcnt = MAXTRANSFER;
	int32_t	nblocks;
	char	*addr;
	struct	scsi_rw_big cmd;
	static	int sddoingadump = 0;
	struct	scsi_xfer *xs = &sx;
	errval	retval;

	addr = (char *) 0;	/* starting address */

	/* toss any characters present prior to dump */
	while (cncheckc() != -1)
		;

	/* size of memory to dump */
	num = Maxmem;
	unit = SDUNIT(dev);	/* eventually support floppies? */
	part = PARTITION(dev);	/* file system */

	sc_link = SCSI_LINK(&sd_switch, unit);

	if (!sc_link)
		return ENXIO;

	sd = sc_link->sd;

	/* was it ever initialized etc. ? */
	if (!(sd->flags & SDINIT))
		return (ENXIO);
	if ((sc_link->flags & SDEV_MEDIA_LOADED) != SDEV_MEDIA_LOADED)
		return (ENXIO);
	if (sd->dk_slices == NULL)
		Debugger("sddump: no slices");
	if ((lp = dsgetlabel(dev, sd->dk_slices)) == NULL)
		return (ENXIO);

	/* Convert to disk sectors */
	num = (u_int32_t) num * PAGE_SIZE / sd->params.secsiz;	/* XXX it must be 512 */

	/* check if controller active */
	if (sddoingadump)
		return (EFAULT);

	nblocks = lp->d_partitions[part].p_size;
	blkoff = lp->d_partitions[part].p_offset;
	/* XXX */
	blkoff += sd->dk_slices->dss_slices[dkslice(dev)].ds_offset;

	/* check transfer bounds against partition size */
	if ((dumplo < 0) || ((dumplo + num) > nblocks))
		return (EINVAL);

	sddoingadump = 1;

	blknum = dumplo + blkoff;
	while (num > 0) {
		pmap_enter(kernel_pmap, (vm_offset_t)CADDR1, trunc_page(addr),
			VM_PROT_READ, TRUE);
		/*
		 *  Fill out the scsi command
		 */
		bzero(&cmd, sizeof(cmd));
		cmd.op_code = WRITE_BIG;
		cmd.addr_3 = (blknum & 0xff000000) >> 24;
		cmd.addr_2 = (blknum & 0xff0000) >> 16;
		cmd.addr_1 = (blknum & 0xff00) >> 8;
		cmd.addr_0 = blknum & 0xff;
		cmd.length2 = (blkcnt & 0xff00) >> 8;
		cmd.length1 = (blkcnt & 0xff);
		/*
		 * Fill out the scsi_xfer structure
		 *    Note: we cannot sleep as we may be an interrupt
		 * don't use scsi_scsi_cmd() as it may want
		 * to wait for an xs.
		 */
		bzero(xs, sizeof(sx));
		xs->flags |= SCSI_NOMASK | SCSI_NOSLEEP | INUSE | SCSI_DATA_OUT;
		xs->sc_link = sc_link;
		xs->retries = SD_RETRIES;
		xs->timeout = 10000;	/* 10000 millisecs for a disk ! */
		xs->cmd = (struct scsi_generic *) &cmd;
		xs->cmdlen = sizeof(cmd);
		xs->resid = 0;
		xs->error = XS_NOERROR;
		xs->bp = 0;
		xs->data = (u_char *) CADDR1;	/* XXX use pmap_enter() */
		xs->datalen = blkcnt * sd->params.secsiz;

		/*
		 * Pass all this info to the scsi driver.
		 */
		retval = (*(sc_link->adapter->scsi_cmd)) (xs);
		switch (retval) {
		case SUCCESSFULLY_QUEUED:
		case HAD_ERROR:
			return (ENXIO);		/* we said not to sleep! */
		case COMPLETE:
			break;
		default:
			return (ENXIO);		/* we said not to sleep! */
		}

		/*
		 * If we are dumping core, it may take a while.
		 * So reassure the user and hold off any watchdogs.
		 */
		if ((unsigned)addr % (1024 * 1024) == 0) {
#ifdef	HW_WDOG
			if (wdog_tickler)
				(*wdog_tickler)();
#endif /* HW_WDOG */
			printf("%ld ", num / 2048);
		}
		/* update block count */
		num -= blkcnt;
		blknum += blkcnt;
		(int) addr += blkcnt * sd->params.secsiz;

		/* operator aborting dump? */
		if (cncheckc() != -1)
			return (EINTR);
	}
	return (0);
}

static sd_devsw_installed = 0;

static void 	sd_drvinit(void *unused)
{

	if( ! sd_devsw_installed ) {
		bdevsw_add_generic(BDEV_MAJOR, CDEV_MAJOR, &sd_bdevsw);
		sd_devsw_installed = 1;
    	}
}

SYSINIT(sddev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE+CDEV_MAJOR,sd_drvinit,NULL)